Method for aerating cement and the like



Nov. 5, 1940. N. AHLMANN 2,220,193 METHOD FOR AERATINC' CEMENT AND THE LIKE I v Filed 0C1. 2', 1957 ZSheets-Shei 1 lNVENTOR Z/m; @/m' V j I ATTORNEYS Nov. 5, 1940. N. AHLMANN METHOD FOR AERATING CEMENT AND THE L'IKE Filed Oct. 2, 1957 2 2 Patented Novr 1940 v I r UNITED STATES PATENT OFFiCE .Mn'rnoD r03 h ifaii grlz cnmnrm THE Q I I I I N Nikolai Amman, i' agenrDenmark, assignor toF. L. Smidth & Company, New York, N. Y.,

a c rporation of New Jersey Application October 2,1937, Serial No. 16, 7 ,042 .In Great Britain October 5, 1936 r s'olaims. (01. 34-24) I, I This invention relates to the cooling of ground from the cement may be effected byintroducing' I hydraulic cement and is concerned more parinto the hot ground cement relatively small" ticularly with a novel method by which ground quantities of air which also aerate the cement and hydraulic cement may be cooled more rapidly and keep it fluent for a short'time, or the cement may, 5 efiiciently than has heretofore been possible. be conveyed pneumaticallyfrom the mill to the 5 Ground cement discharged from the grinding cooler, the aeration being effected by the'air emmill must be cooled before being placed in the ployed for'conveying. In the first instance, the storage silos and various methods and apparatus amount of air introduced into the cement dehave been employed for the purpose.. In certain pends upon the amount of water vapor to be ex- 10 forms of such apparatus, the ground product is pelled, but in general, from two' to five litres of 10 cooled in a chamber which-has a heat conducting atmospheric air per' kilogram of cement is suffiwall, along one surface ofwhichthe cement is 01cm; In the latter .case; the amount of air moved by appropriate means, while the other surusually employed for conveying cement pneuface is cooled by means of a cooling mediummne matically isof the order of '25 to 50 kilograms 5 form of apparatusof the type referred to being per kilogram of cement, and such an amount of illustrated in my co-pending application, Serial air has been found sufficient in practice to r'e-- No. 79,837, filed May 15, 1936. .In the cooling move substantially all of thewater vapor'frorn. operation carried'on by the use of this and simthe cement before the latter reaches the cooling ilar apparatus, difilculties have been encountered apparatus. 7 I r v i in keeping the cooler clean. and in condition to e, method of the invention-is quite different 20 eff ct good at exchangee cause of t s from that employed in'cooling cement clinker isdifiiculty is the condensation on the cooling sursuing from the kiln. To coolclinker, the amount face of water vapor (including steam) present in of air required is aboutone'hun'dred times asv the cement which causes the cement to stick to great as that necessary to aerate cement and the surface. Even if the cement is groundenrender it fluent by introduction of small quan- 25 tirely' from dry clinker, such difficulties arise betities of air. Accordingly, the" apparatus emcause gypsum is always ground in the mill with ployed in the practice of the present invention the cli r a d part f t wat r f crysta zamay include a container for the cement, which tion of the gypsum is convertedinto steam, ,which has afew air nozzles through which air is blown IV is Present in e und material disc g at a suflicient velocity to prevent the" cement 30 from the mill. falling through them; the total cross-sectional Accordi to-t e pres nt invention, these difarea of the nozzles amounting to only qa small ficulties are overcome by removing the water vafraction of the total area of the portion "of the por from the hot ground cement before it is container covered by the'cement; Withfsofew cooled. For this purpose the cement, in its pasair nozzles in use, means are provided in -.the 35 sage from the mill to the silos, is aerated in an container for" stirring the cement to effect the appropriate manner to such an extent that the desired aeration and the aerated product leaving water vapor is displaced therefrOm and therethe container isjthen delivered to a cooler in after the cement is cooled in heat exchange ap- 'whic h'it passes along one surface of a heat con- 40"Daratus of thetype, above referred to. The elimi- I ucti Wall, the other surfaceof which is cooled 4 nation of the water vapor fromthe hot material y a lin e u d f employing a prevents it from stickingto the surfaces of the container with air nozzles,- one wall of thereoncooler and the .efficiencyof the cooling process taihel y be formed of P a the is thereby greatly increased. 7 I I pores of which are'so small that .thewcement In the practice of theinvention, the air used cannot passj therethrough. Compressed air 1e for aeration is preferably introduced intov the then passed through the pores into the cement' cement under pressure butthe displacement of to aerate the latter." v v I v the water vapor may be efiected by the use of a In a modified form of the invention, the hot vacuum, if desired. Also, since the cement must ground cement issuing from the mill is conveyed ordinarily becooled somewhat before condensapneumatically to the cooler and the conveying 60 tion takes place, it is within the scope of the insystem includes a' cyclone or similar separator ventiontopermit such initial cooling to occur and by'which the air introduced into the cement is to remove the-final part of the waternvapor. durremoved therefrom prior to the introduction of E the al cooling. I the cement into the cooler; Inthe use of this The displacement of the water vapor or steam apparatus, the conveying air serves to aerate the 55' cement and to displace the water vapor therefrom.

For a better understanding of the invention, reference may be had to the accompanying drawings, in which 1 Figure 1 is a longitudinal sectional view of one form of aerating apparatus employed in practicing the invention;

Figure 2 is a similar view of a modified form of aerating apparatus; and

Figure 3 is a diagrammatic illustration of a form of apparatus used for practicing the invention, in which the cement is conveyed pneumatically.

In the practice of the invention by means of the apparatus illustrated in Figurev l, the hot ground cement issuing from the mill is introduced through an inlet l0 into a trough-like con- 7 Is by which it may be connected to a source of an outlet 20.

duced into the cement through a power. At the end of the container oppositeto that provided with the inlet is an outlet l'l.

The apparatus illustrated in Figure 2 includes a trough-like container [8 having an inlet l9 and Within the container above the lower wall thereof is an inner bottom wall 2| formed of porous material having very fine pores.

Partitions22 leading from the lower Wall of the container to the inner porous wall subdivide the space between the walls into chambers 23 into each of which air is supplied under pressure by a pipe 24 having branches 25. a T

In the use of the apparatus shown in Figures 1 and 2, the hot ground cement from the mill is introduced into the container ll, l8 through the inlet thereof and movesalong the container to the outlet [1, 20. Air is introduced'into the layer of cement in the container in a quantity which I is relatively small bu t sufficient to effect the desired aeration of the material. The introduction of the air, as described, displaces the water vapor including steam present in the cement, the vapor escaping through the open top of the trough. In the apparatus shown in Figure 1, the air is introsmall number ofnozzles and accordingly, to effect the desired aeration, a stirring means is provided. In the apparatus shown in Figure 2, the air is introduced into the cement through a multiplicity of fine pores and the distribution of the air is such that the desired aeration is accomplished without the use of stirring means.

The aerated cement issuing from either container, shown in Figures -1 and 2, is then conveyed to a cooler of suitable construction, in which the cement may move along one surfaceof a heat conducting wall, on the outer surface of which is maintained a cooling medium. Various types of apparatus may be employed for the purpose, such, for example, as that shown in my co-pending applicationabove identified. The cooled cement issuing from the cooler is then delivered to the silo forstorage. 1 v

In practicing .the invention by the apparatus illustrated in Figure 3, the cement ground in the mill 26 is delivered by a suitable conveyer 21 into the conveying chamber'28 of a pneumatic conveying system. Compressed air is supplied'to this chamber by a compresser 29 through a pipe 30, the air being admitted after thechamber is filled and serving to aerate the cement and discharge it through a conduit 3| leading to a separator 32, illustrated as being of the cyclone type. The greater part of the air then leaves the separator through the outlet 33, carrying with it substantially all the water vapor present in the cement when it left the mill 26. The cement itself leaves the separator through the bottom outlet and enters a conveyer 34 leading'to a cooler 35. The cooler is illustrated diagrammatically in the drawings and, as shown, it includes wall 36 of generally conical shape with its smaller diameter at the lower end. The cement is fed into the lower end of the cooler and as it enters into the cooler, it is acted on by vanes 31 mounted on radial arms 38 on a shaft 39 so that the cement travels upward ina layer along the wall 36 in a helicalpath. The wall 36 is of heat conducting material and the cooling medium is maintained 0 against itsouter surface. For this purpose the cooler may be provided with water pipes 40 having discharge 'nozzlesby which cooling water is delivered against the outer surface of the wall 36, and flows downwardly thereon. The cement which has been cooled in the cooler enters a conveyer 4| of conventional type and is conveyed thereby into a silo 42.

In the practice ofthe invention by any of the forms of apparatus disclosed, the ground cement discharged from themill is transferred to storage and on the wayto the silos, it is first aerated to displace thewater vapor including steam therefrom and is then cooled by passage through a heat exchange type of cooler.- Since the water vapor is'substantially entirely removed from the cement beforeit enters the cooler, the cement has no tendency to adhere to the walls of the latter. As a consequence, proper flow of the cement through the cooler is obtained and the cooling is effected with-high heat efficiency through the clean cooling surface. 1

I claim: v

1. A method of cooling ground hydraulic cement which comprises :introducing air into the hot ground cement to displace water vapor therefrom, and then passing the aerated cement in a thin'layer along one surface of a heat-conducting wall and maintaining a coolingmedium in contact with the other surface of the wall.

2. A methodof cooling ground hydraulic cement which comprises introducing air in relatively small quantity into the hot ground cement to displace water vapor therefrom and render the cement fluent, and then passing the aerated cement in a thin layer along one surface of a heat-conducting wall and maintaining a cooling medium in contact with the other surface of the wall.

3. A method of cooling ground hydraulic cement which comprises transferring the hot ground cement from the place of grinding to a place of storage, and while the cement is thus beingtransferred, introducing air into it to displace water vapor therefrom, and thereafter withdrawing heat from the cement by passing the cement ina layer along a heat-conductive dium'in contact with the other surface of the wall.

5. A method of cooling ground hydraulic oement which comprises conveying the hot ground cement from the place Where "the grinding was done, introducing air into the cement being conveyed to displace water vapor therefrom, and thereafter moving the 1 aerated cement along a surface and withdrawing'heat fromthe cement 10 through the surface.

from the conveying air and water vapor, and

thereafter moving the aerated cement along a surface and withdrawing heat from the cement I through the surface.

NIKOLAI AHLMAN'N. 10 

